This invention relates in general to mail sorting equipment and more particularly to an improved elevator for the code reader of a high speed automatic mail sorting machine.
High speed mail sorting machines have recently gained considerable popularity, due in large part to the increasingly large volume of mail that must be handled daily by the postal service, modern businesses, governmental units and other large institutions. An automatic mail sorting machine typically includes a feeder device which receives a stack of envelopes and feeds them to a pick off mechanism which picks the individual envelopes off of the stack and delivers them one at a time past a code reading device. As the envelopes are conveyed past the reader, it reads coded indicia on the envelopes such as zip codes or bar codes. Electronic sorting circuitry then controls deflector gates or other diverter devices which direct the envelopes into separate sorting bins corresponding to the coded indicia. In this manner, all envelopes having the same code are deposited in the same bin or bins of the mail sorting machine.
As previously indicated, sorting information in coded form is imprinted on the envelopes and is read by the code reading device. Zip codes are often used as the coded indicia so that outgoing mail can be sorted into groups of envelopes having a common destination. Alternatively, coded information representing the different departments within a large business or governmental entity can be used to facilitate the routing of incoming mail to the proper department. The coded information is usually in the form of a magnetic code or a bar code. Magnetic reading devices are used to read the magnetic code, while optical code readers are normally used to read the bar code.
In either case, it is desirable to provide for adjustment of the elevation of the reader in order to compensate for the differences in the location of the coded indicia. For example, if the machine handles envelopes that differ in size, the zip code or bar code information can be at a different elevation for each different sized envelope. Even envelopes having the same size sometimes have the code imprinted at different elevations for different batches of mail. Accordingly, the reader device must be capable of being moved up and down in order to properly align with coded indicia at various elevations. The range of movement should be great enough to accommodate the widest difference in position of the codes, which may vary by up to about three inches.
In the past, elevators have been devised to permit adjustment of the elevation of the reader. However, the known elevator devices have performed in a less than satisfactory manner in a number of respects. Perhaps most notably, the slow speed at which existing elevators operate has been a problem. The code reader is mounted on a plate or platform which is moved up or down by screw drives connected with the corners of the platform. An electric motor drives the screws through a chain and sprocket drive system. With this type of arrangement, the code reader head is moved up and down so slowly that it can take up to five minutes for the reader to be moved between extreme positions. As can easily be appreciated, this causes significant delays in the adjustment of the code reader and slows down the mail sorting operation accordingly.
Another problem with existing elevator devices is that human error can cause misalignment of the reader unit. Typically, the operator of the machine must operate a manual switch which activates the motor and causes the reader to be moved until it is perceived as being at the proper height, as indicated by visual alignment of a pointer or other indicator with the coded information on the envelopes that are to be handled. The switch is then released and the motor stops. This procedure is not only cumbersome and time consuming, but it also often leads to errors in alignment due to the parallax that is involved in attempting to visually align the pointer with the code on the envelopes.